What a difference a temperature range can make! Some plain carbon steels, some martensitic (quenched) carbon and alloy steels, and some high Chromium content steels can become embrittled if the wrong temper temperature is used.
This means premature failure in impact applications. Blue Brittleness
Upon heating some plain carbon and alloy steels-not necessarily those that have been quenched to martensite or bainite-can exhibit both an increase in strength and a substantial decrease in ductility/ impact strength.
In this low temperature range, we call this effect blue brittleness.
Blue Brittleness is a strain aging mechanism that occurs in this blue heat temperature range.
Martensitic (Quenched) steels can become embrittled if the wrong temper temperature is used.
Link to graph. In the range of 700 to 1070 degrees F ( 375 to 575 degress C) most common low alloy steels show an increase in their ductile to brittle transition temperatures- regardless of whether they are heated into this range, or slowly cooled through it. (Think large section parts/weldments). Lower Manganese (below 0.30 wt %) containing plain carbon steel grades do not seem to be susceptible, although elevated levels of Tin or Phosphorus can make even these grades somewhat suceptible. For these reasons, we would NOT use any tempering cycle below 1100 degrees F (~595 degrees C) for the common carbon and alloy constructional steels typically designated by AISI and SAE in North America. This gets us past the ductility troughs seen on the above figure. 500 Degree F Embrittlement
500 degree F Embrittlement also occurs in quenched and tempered High Strength Low Alloy (HSLA) steels when they are subjected to a temperature range between 400- 700 degrees F (~ 200-370 degrees C). This differs from Blue Brittleness in that it is a phenomenon of tempered martensite, it is not related to strain aging. I was taught that it is rather a result of precipitation along prior austenitic grain boundaries.
Proper selection of steel chemistry is the best defense against this type of embrittlement, with Aluminum additions above 0.1 weight % usually effective at preventing the problem. (Some steel producers lack the ability to add Aluminum to their steel melt due to technology constraints on their casters…) 400 to 500 Degree C Embrittlement
If the steel is high Chromium content (15% or more by weight) it can be subject to embrittlement when held in a 400-500 degree C (~750 -930 Degrees F) range for a long enough time. (Think heat affected zone in welding Stainless steels.)
This embrittlement can be eliminated by a proper soak at a higher temperature to redissolve the carbide (and possibly nitride?) precipitates. Conclusion
These are the primary forms of embrittlement that I have encountered in my career. Other types of embrittlement can include Liquid Metal Embrittlement, Sigma Phase Embrittlement and Embrittlement driven by neutron irradiation, or environmental factors such as hydrogen absorption, (often in plating) or Stress Corrosion Cracking where outside chemical attack and mechanical stress produce fine cracks in the steel. Bottom line: Thermal treatments, and post quench temper treatments below 1100 degrees F are not recommended because of their possible embrittling effects on susceptible steel grades in common use in North America.
With increasing temper temperature, the plasticity of a quenched martensitic structure increases up to around 400 degrees F; decreases to a minimum in the 450-700 degree F (230-370 degrees C) range, and then continues to increase.
As an American, a dad, a son, a husband, a professional, and as a guy, I have much to be thankful for. I am grateful that the member companies of the PMPA continue to find value in my work. It is the basis of my family’s economy. I am grateful for the service of the men and women of the armed forces, my daughter and son in- law included, who put duty, honor and country ahead of all the stuff in my list below.
I am thankful that I was born an American and am thankful that my life choices have resulted in a life worth contemplating. I hope you’ll take a few minutes this Thanksgiving Day to contemplate what makes your life worth living too. A few of the things I am thankful for include: Still having a couple of $20’s in your wallet the day before payday. Nobody in front of you in the passing lane. Waking up after surgery. The smell and taste of the summer’s first burgers on the Grill. A high draft number. Honest gratitude when your kid says “Thanks Dad.” Solving a million dollar process problem with your brain, and a pencil and paper. New Friends. OLD FRIENDS. Meals by Candlelight. Dropping the deer with a clean single shot using iron sights. It’s A Girl.^2 It’s A Boy. The whole body wiggle and smile you get when the baby sees that you are going to pick them up. The squeal in your little girl’s voice when she realizes that you aren’t holding her bike up… Having a customer you haven’t heard from in years track you down in another state to ask your opinion. The sound of the carabiner snapping onto the bungee cord at the top of the tower. Being able to say “We handled that,” when the boss rushes in with that look in his eyes. Great optics, space on the chip, and adquate light. Being elected president of the club that didn’t want to let you join. Hearing the piano coda in Layla emerge from the layers of guitar. The smell and feel of real leather- work gloves or baseball gloves. Flying to Washington D.C. with the CEO to handle “That Department of Commerce issue.” Strawberries from your own garden. The flash of headlights in the driveway 5 minutes before your daughter is due back from her date. A graph that makes sense. Getting the tool on center with the first ‘tap.’ Hearing Carlos Santana bend and sustain a high guitar note for what must be 200 heartbeats. Pepsi right out of the fountain. The thoughtful email you get in the middle of a 7 alligator morning from your friend who “just knew.” New Books. Old Books. Solving a problem that no one else in your industry has ever solved. The wind and scenery rushing by as you pedal your bike. Not winning the election, but having received the endorsement of the local paper and the Chamber of Commerce. Watching your son put on an exhibition on how to play first base during a playoff game. The awe in your father’s eyes when you show him the plant that you run. Hearing the change in her voice when she realizes it’s you on the phone. Watching your kids graduate and knowing that their grades were WAY better than your own. The look on your daughters’ faces as they started down the aisle with you, when you tell them how many heartbeats they had had since you first welcomed and loved them into our world. Eliminating the root cause forever as a result of what you learned from your designed experiment. Kneeling at the Liberty Bell in Philadelphia, in your suit, while on a break from a trade show, taking a moment to reflect and be thankful for all of your blessings, and all of your problems, happiness, and tribulations, while a busload of foriegn tourists try to figure out what the heck you are doing. Happy Thanksgiving! I am grateful the members of the PMPA continue to find value in the work that I do for them. It is the basis of my family’s economy.
When its all about delivery, how many SKU’s of raw material can your shop effectively manage?
Precision machining shops have been applying 5-S principles in operations for a number of years.
PMPA’s NATIONAL TECHNICAL CONFERENCE in 2003 featured a session on Lean setup’s that focused on a 5-S approach. But applicability of lean tools and 5-S isn’t limited to only shop operations. The raw material procurement process seems like a great place to try to lean your system and improve your competitive advantage by saying “yes” quicker than the shop waiting for a specific size of barstock.
With materials markets and customer demand in a very confounding state, now is a great time to apply 5-S to your raw material procurement system. Here’s How: Sort your material requirements into material grade and size categories. With today’s prices and longer lead times, minimizing the number of specific sizes that you need per grade will get you to yes quicker than waiting for each particular starting size of bar stock. This will permit flexibility to make parts from the same grade in a similar size range from two or three stock sizes rather than having five or six item-specific sizes to order, inventory, track and expedite. Straighten your existing materials inventory and orders to give you a clear view of your raw material on hand and on order. Can any of your “orphan items” be applied to make another product. You need to know your inventory. Sweep your inventory and order book of unnecessary items and orders. Will having a material “tag sale” make sense on items that you are unlikely to use? Standardize your material order procedures and quoting process. You want to consistently order materials that can be used for multiple-applications, in easier to find standard sizes. You are not well served by trying to manage multiple orders of long lead time-specific items. This is where engineering can add real value to your company! Create a team to determine your needs by reviewing order book and customer commitments as well as supplier lead times and flexibility. Sustain the process. Now that you have done all you can to minimize waste in your system of excess material item counts, it’s time to get customers to help you to further reduce the waste. Show your customers how you are standardizing stock sizes to minimize lead time and maximize your ability to say “yes.” Ask for their assistance to help shrink the negative consequences by giving you firm commitments that reflect the material market’s lead times. Then you and they can be more confident in your ability to meet their ever changing needs.
Applying the 5-S system to your material procurement system will create savings that should more than cover the increased yield loss of the additional stock removal:
It will also help you get a higher percentage of quotes, as you will be able to quote earlier delivery dates than someone who has to find a particular starting size in the market.
I think that when you see your customers accept your price for soonest delivery (based on an appropriate price that reflects the cost to whittle the part out from a larger-diameter “mother size”) you will be convinced that it is delivery not price that is driving todays customers.
How much can you save if you reduce the number of raw material items on hand, increasing inventory turns? Less is more. What is the cost to place and follow up a purchase order? To hold multiple items in inventory? What are your current inventory turns? What should they be?
Bernanke Is Right Chinese Mercantilism, Not Fed Easy Money, Are Making a Mess
Guest post by Peter Morici
Ben Bernanke is right. Germany shouldn’t blame easy money in the United States for the world’s woes. Currency mercantilism in China and elsewhere is causing a mess-especially in the United States.
Last week, Bernanke fingered China, Taiwan, Singapore, and Thailand for driving down the values of their currencies. Through massive government purchases of U.S. Treasuries securities, those mercantilists accomplish huge trade surpluses and jack up their GDP growth and employment. The flip side is a huge U.S. trade deficit that sentences Americans to slow growth and 10 percent unemployment. Sadly, such mercantilism makes free trade an unworkable strategy for the United States.
Global demand for goods and services has become so distorted by subsidized Asian exports that workers in the United States face terribly high unemployment. Add in those stuck in part-time jobs that would prefer full time work, and the United States is losing the productivity of at least 10 million workers. At about $100,000 per worker, that adds another $1 trillion, bringing total lost productivity to about $1.3 trillion dollars. Ben Bernanke estimates U.S. capacity underutilization at about 8 percent-that comes to the same $1.3 trillion. Amazing!
At the recent IMF meetings, Treasury Secretary Geithner asked European allies for help in persuading China to revalue the yuan. Led by Germany, the United States was told to pound salt and instructed to slash its budget deficit and tighten monetary policy.
No surprise. Germany enjoys huge trade surpluses with a euro that is undervalued for its economy, because it is lumped into Euroland with weak Portugal, Ireland, Greece, Spain and Italy. Germans live well and impose austerity and unemployment on those neighbors. Berlin doesn’t want any sacred mercantilist cows slayed, lest its own ruse get discovered.
If the United States cut its budget deficit in half and raised domestic interest rates two percentage points, U.S. consumption and imports would crash, unemployment would rocket to 15 percent, and a global depression would result whose horrors we all thought were long ago buried in history books. If China and Germany won’t be reasonable, the United States is really left with no option but to take direct action to balance its trade. China’s government purchases to suppress the yuan come to about 35 percent of GDP and provide a subsidy on exports of similar amount. Washington should even things up by imposing a comparable tax on purchases of yuan and euro for the purpose of importing from or investing in China and Germany, until their leaders agree to engineer an orderly revaluation of currencies and trade.
The Chinese and Germans shouldn’t care-after all, the Americans are nothing but whining spendthrifts whose problems are of no import. They would scream bloody murder anyway.
Beneath the howls, domestic demand and employment in the United States would fire up, manufacturing would flourish, GDP growth rise to about 5 percent, and unemployment would fall to a similar figure.
The extra growth would eventually balance the U.S. budget, as it did during the Clinton years. Once China, Germany and others agreed to a realignment of exchange rates and the tax ended, all nations would benefit from trading with a more rapidly growing and stable U.S. economy. Peter Morici is a professor at the Smith School of Business, University of Maryland School, and former Chief Economist at the U.S. International Trade Commission.
Gotta love the entrepreneurial spirit of engineers vs. the bureaucratic regulators (aka Forces of Evil…)
To improve energy efficiency and reduce greenhouse gas emissions, the EU has banned the sale of incandescent light bulbs of over 60 watts.
Enter the engineers.
Engineer Siegfried Rotthaeuser studied the EU legislation and realised that because the inefficient old bulbs produce more warmth than light they could be sold legally as heaters.
Rotthaeuser is legally importing and distributing 75 and 100 watt light bulbs — by producing them in China, importing them as “small heating devices” and selling them as “heatballs”. Check out the heatball website here. What is the Heatball Manifesto? A heatball is electrical resistance, used as a heater. Heatball is a campaign of opposition against regulations being passed that bluntly ignore the most basic democratic principles. Heatball also resists unreasonable measures supposedly protecting our natural environment. How can we be made to believe that using energy saving lamps will save our planet, while at the same time the rain forests have been waiting in vain for decades for effective sustainable protection? Heatball is electrical (and political) resistance. Viva la resistance!
PMPA’s Index of Sales of Precision Machined Products in October 2010 was 103, basically at the six month average of 103.66.
We see the lack of a clear trend as the index continues to hold within a band of 97 to 107 over the past six months as indicative of the “New Normal”- sales levels recovered to those of the beginning of the decade. The MSCI data for October 2010 showed that distributor shipments of steel were up 15.8% more than October 2009. The SAAR for light vehicle production reached 12.26 million, the best non-rebate fueled sales results since September 2008.
The current issues in the banking and housing sector are likely to keep our hopes of a home building recovery in check, and our industry’s shipments will continue to be dominated by Automotive, Armament, Aerospace and others.
We were encouraged to see that the 3 month moving average rose slightly in October. Our shop managements continue to show their savvy; October hours of first shift worked declined .4 to 43.1 from September 43.5. Only 2% of reporting companies are scheduling a first shift of less than 40 hours. This data explains why we remain optimistic about the Precision Machining Industry Outlook for North America in the short term.
For more information, PMPA members can download the October 2010 report here.
Press contact Miles Free at PMPA
Post by James Pryor II American Safety And Health Management Consultants, Inc.
Your shops’s LOCKOUT /TAGOUT program is the “key” to safety on machinery and equipment repair and maintenance operations.
An effective and stringent LOCKOUT/ TAGOUT program provides critical protection for employees during repairs and maintenance.
Here are a few checklist items to evaluate your Lockout Tagout program. 1. Review OSHA 29CFR1910.147 the Federal Lockout/Tagout regulation. 2. Review Requirements for Lockout/ Tagout devices- they must be durable, standardized, substantial and identifiable. 3. Review all equipment requiring Lockout/Tagout- for example Locks, Blocks, Chains, Multi lock hasps and other devices. They must be durable, standardized, substantial and identifiable. 4. Review your procedures for equipment where Lockout/Tagout is required. 5. Insure AFFECTED and authorized employees are trained in Lockout / Tagout procedures initially and annually thereafter. 6. Insure training for both AFFECTED and AUTHORIZED employees is conducted whenever there is a change in equipment or procedures. 7. Keep employees informed when equipment is being repaired or serviced . 8. Stay alert and use common sense when Lockout/ Tagout procedures are in place. 9. Keep written records of all Lockout Tagout Hazardous Energy Control Training. 10. And of course, every time you are out in the shop make certain that your team is following your procedures.
Are they being followed ? Are they effective? What is the best way that you have found to convince employees of the importance of hazardous energy control? Kirlian Key Photo Credit
Aluminum is a critical ingredient of steel in our shops, not just as a stand alone material for machining.
Aluminum metal is used to make many parts produced by precision machining, and is finding increasing application in automotive because of its light weight and high strength to weight ratio.
But aluminum plays a key role in some steel applications that you should know about.
Aluminum is used as a deoxidizer. Aluminum scavenges Oxygen from the melt reducing porosity in the solidiied steel.
Aluminum is used to produce a fine austenitic grain size. (Aluminum is the most effective element to control grain growth in steel.)
Aluminum is also used as an alloying addition in the amounts of 0.95- 1.30 weight 5 to make Nitriding steel. Nitriding increases the hardness of the steel by the formation of a hard, stable aluminum nitiride compound.
Aluminum’s ability to scavenge Oxygen results in tiny aluminum oxide particles dispersed throughout the steel. As aluminum oxide is hard and abrasive, Aluminum is not deliberately added to free machining steels where it would destroy tool life. Aluminum is more effective at grain growth control than elements like vanadium, titainium and zirconium. These three elements adversley affect hardenability because they form carbides that are both quite stable and difficult to dissolve in austenite prior to quenching.
In the nitriding steel, this recipe is relatively distortion free at the temperatures up to the nitriding temperature.
So yes Virginia, you may have more Aluminum in your shop than the number of aluminum bars, soda cans and foil wrappers might lead you to believe. Hiding in your steel! Nitride structure Nitralloy Table
“Management by objectives works if you know the objectives . Ninety percent of the time, you don’t.” – Peter Drucker
Today, we live in a time of breathtaking rate of continuous change.
Yet we crave stability. Something solid to hang on to.
Despite the rapid pace of change, and its gut wrenching consequences, we can find that stability we crave.
Its called the mission. The mission is the central, continuous thought that the changes (whatever they might turn out to be) that we implement are meant to preserve.
Our mission is our “fundamental purpose” for being; for doing what we do.
Mission statements answer the question “Why?”
Objectives are how our organizations achieve their mission.
Objectives are measureable, time delimited, and answer the question “How?”
Our mission here at PMPA is to “provide information resources and networking opportunities that advance and sustain our members.”
Mission answers “WHY?” Objectives are measureable, time delimited and answer the question “HOW?” “By getting this blog out for Thursday, I will have provided information and resources to sustain my members.” When faced with change, the first thing that I would do have done is review the mission with my team. Because… The mission answers “Why?”
Or as we learned in Mrs Ponte’s Latin Class SO many years ago… “Our plans miscarry because they have no aim. When a man does not know what harbor he is making for, no wind is the right wind.”-Seneca the Younger What is your mission? More importantly what does your team think your mission is?
Counting parts with scales is not rocket science. But getting the accuracy in the count done efficiently is a challenge akin to a moonshot if you are the person that has to resolve the piece count discrepancy paperwork…
Principle and benefits of piece counting with a scale
Application areas of piece counting solutions
Challenges associated with counting
Solutions and best practices
The second webinar Smart Weighing Solutions for Lean Production will show you how to minimize waste using accurate scale based counting systems and Statistical Quality Control.
The first half is a nice review of Mettler’s own lean journey in manufacturing.
The second half has a number of case studies regarding parts, shops, and customers like ours. We see on time delivery and significant reduction in stock inventories as the primary advantages of using such systems. Plus you will save time and money.
We relied on Mettler technology in the labs that I worked in.
I’m forwarding you these links to maybe help you
Find a better weigh… Mettler Toledo offers two free, on demand webinars that will help you understand (and resolve) the issues of using scales to accurately count component parts.